The present disclosure relates to an imaging apparatus. More particularly, the present disclosure relates to an imaging apparatus controlling an operation to drive a lens and also relates to a processing method adopted by the apparatus as well as a program executed by a computer to implement the method.
An imaging apparatus has been becoming popular. A typical example of the imaging apparatus is a digital still camera for taking an image of an imaging object such as a human being by making use of an imaging device, generating the taken image and recording the taken image. In addition, an imaging apparatus having an autofocus function has also been becoming popular too. On top of that, with downsizing of components such as imaging devices and optical-system members, a portable information terminal including any of such imaging devices as a camera module has also been becoming popular as well.
Such a portable information terminal employs an actuator for moving a focus lens in the direction of the optical axis in order to implement the autofocus function. It is desirable to have an actuator that moves the focus lens by a distance linearly proportional to a voltage applied to the actuator. In order to reduce the amount of power consumed by the actuator and the size of the actuator, however, more and more portable information terminals employ an actuator which has a hysteresis characteristic representing a relation between the voltage applied to the actuator and the movement quantity of the focus lens.
If an actuator having a hysteresis characteristic representing a relation between the voltage applied to the actuator and the movement quantity of the focus lens is used, however, an accurate movement quantity cannot be obtained because an error is generated in the movement quantity. In order to solve this problem, a focus control technology has been introduced as a technology for improving precision of positioning the focus lens by compensating the movement quantity for such an error and this focus control technology has been becoming popular. To put it in detail, in the case of an actuator having a hysteresis characteristic, a sensor for detecting the position of the focus lens is provided for carrying out feedback control to adjust the movement quantity. However, the sensor for detecting the position of the focus lens is a hindrance to an effort to reduce the size of the imaging apparatus and raises the cost of the apparatus. For this reason, we have been studying an imaging apparatus employing an actuator having a hysteresis characteristic and making use of no sensor for detecting the position of the focus lens.
For example, there has been proposed an imaging apparatus which controls the position of the focus lens by measuring the position of the focus lens by making use of a counter carrying out a counting operation during the time period to apply a voltage to a piezoelectric device serving as the actuator. For more information on such an imaging device, the reader is advised to refer to documents such as Japanese Patent Laid-open No. 2009-169013.